The powder metallurgy of today calls for improving the technological processes and poses high demands on the cost efficiency and quality of the end products obtained thereby. Porous materials are the subject of special attention in the art of powder metallurgy. In this connection, one very promising trend is the use of metal fibers instead of metal powders. However, a wider application of metal fibers in powder metallurgy is hindered by the lack of sufficiently simple and inexpensive production processes.
A cardinal solution to the problem may be offered by obtaining metal fibers directly from a metal powder by treating the powder mechanically.
There is known a method of making metal fibers from spherical particles of a metal powder (cf. International Application PCT/SU 82/00030, filed Sept. 15, 1982) comprising the steps of feeding the spherical particles of metal powder, subjecting these particles to deformation by rolling each of the particles in the path of the process and simultaneously stretching or elongating such a particle along the axis of its rotation, and discharging metal fibers thus obtained.
The same application further describes an apparatus for making metal fibers from spherical particles of a metal powder to practise the above method. The apparatus comprises a mechanism for feeding the spherical particles of metal powder provided with feeding passages, and a deforming or sizing tool which is comprised of one element having the form of a main roll and another element; the two elements of the deforming tool are disposed one relative to the other for rolling and stretching the spherical particles of metal powder being deformed, these particles being fed into a clearance between the two elements from the feeding passages of the feeding mechanism.
However, the above method and apparatus for making metal fibers suffers from a disadvantage in that for attaining a maximum possible ratio between the length and the diameter of fibers produced from the spherical particles of the metal powder limited exclusively by the plasticity of the metal of the particles an excessive number of rolling cycles is required. This results in reduced production efficiency and affects the plasticity of the metal of the powder particles due to cracks tending to develop therein. Stretching along the axis of rotation of the deformable spherical particles of metal powder fails to completely neutralize the braking effect of the contact friction forces directed in parallel to the axis of rotation toward the center of the fiber being formed and hampering the deformation of the particles, since the rate of such stretching fails to match with the rate of plastic flow of metal in elongation of the fiber.